Abstract

Light nuclei were created during big-bang nucleosynthesis (BBN). Standard BBN theory, using rates inferred from accelerator-beam data, cannot explain high levels of 6Li in low-metallicity stars. Using high-energy-density plasmas we measure the T( 3He,γ) 6Li reaction rate, a candidate for anomalously high 6Li production; we find that the rate is too low to explain the observations, and different than values used in common BBN models. As a result, this is the first data directly relevant to BBN, and also the first use of laboratory plasmas, at comparable conditions to astrophysical systems, to address a problem in nuclear astrophysics.

@article{osti_1341857,
title = {Using inertial fusion implosions to measure the T+He3 fusion cross section at nucleosynthesis-relevant energies},
author = {Zylstra, Alex B. and Herrmann, Hans W. and Johnson, M. Gatu and Kim, Yong Ho and Frenje, J. A. and Hale, Gerald M. and Li, C. K. and Rubery, M. and Paris, Mark W. and Bacher, A. and Brune, C. R. and Forrest, C. and Glebov, V. Yu. and Janezic, R. and McNabb, D. and Nikroo, A. and Pino, J. and Sangster, T. C. and Seguin, F. H. and Seka, W. and Sio, H. and Stoeckl, C. and Petrasso, R. D.},
abstractNote = {Light nuclei were created during big-bang nucleosynthesis (BBN). Standard BBN theory, using rates inferred from accelerator-beam data, cannot explain high levels of 6Li in low-metallicity stars. Using high-energy-density plasmas we measure the T(3He,γ)6Li reaction rate, a candidate for anomalously high 6Li production; we find that the rate is too low to explain the observations, and different than values used in common BBN models. As a result, this is the first data directly relevant to BBN, and also the first use of laboratory plasmas, at comparable conditions to astrophysical systems, to address a problem in nuclear astrophysics.},
doi = {10.1103/PhysRevLett.117.035002},
journal = {Physical Review Letters},
number = 3,
volume = 117,
place = {United States},
year = {2016},
month = {7}
}

Few-body nuclear physics often relies upon phenomenological models, with new efforts at the ab initio theory reported recently; both need high-quality benchmark data, particularly at low center-of-mass energies. We use high-energy-density plasmas to measure the proton spectra from 3He + T and 3He + 3He fusion. The data disagree with R -matrix predictions constrained by neutron spectra from T + T fusion. Here, we present a new analysis of the 3He + 3He proton spectrum; these benchmarked spectral shapes should be used for interpreting low-resolution data, such as solar fusion cross-section measurements.

The creation of carbon and oxygen in our Universe is one of the forefront questions in nuclear astrophysics. The determination of the abundance of these elements is key to our understanding of both the formation of life on Earth and to the life cycles of stars. While nearly all models of different nucleosynthesis environments are affected by the production of carbon and oxygen, a key ingredient, the precise determination of the reaction rate of 12C (α, γ) 16O , has long remained elusive. This is owed to the reaction’s inaccessibility, both experimentally and theoretically. Nuclear theory has struggled to calculatemore » this reaction rate because the cross section is produced through different underlying nuclear mechanisms. Isospin selection rules suppress the E 1 component of the ground state cross section, creating a unique situation where the E 1 and E 2 contributions are of nearly equal amplitudes. Experimentally there have also been great challenges. Measurements have been pushed to the limits of state-of-the-art techniques, often developed for just these measurements. The data have been plagued by uncharacterized uncertainties, often the result of the novel measurement techniques that have made the different results challenging to reconcile. However, the situation has markedly improved in recent years, and the desired level of uncertainty ≈ 10 % may be in sight. In this review the current understanding of this critical reaction is summarized. The emphasis is placed primarily on the experimental work and interpretation of the reaction data, but discussions of the theory and astrophysics are also pursued. In conclusion, the main goal is to summarize and clarify the current understanding of the reaction and then point the way forward to an improved determination of the reaction rate.« less

Full calculations of six-nucleon reactions with a three-body final state have been elusive and a long-standing issue. We present neutron spectra from the T(t,2n)α (TT) reaction measured in inertial confinement fusion experiments at the OMEGA laser facility at ion temperatures from 4 to 18 keV, corresponding to center-of-mass energies (E c.m.) from 16 to 50 keV. A clear difference in the shape of the TT-neutron spectrum is observed between the two E c.m., with the 5He ground state resonant peak at 8.6 MeV being significantly stronger at the higher than at the lower energy. The data provide the first conclusivemore » evidence of a variant TT-neutron spectrum in this E c.m. range. In contrast to earlier available data, this indicates a reaction mechanism that must involve resonances and/or higher angular momenta than L = 0. Furthermore, this finding provides an important experimental constraint on theoretical efforts that explore this and complementary six-nucleon systems, such as the solar 3He( 3He,2p)α reaction.« less

smore »Background: We preent that K 40 play a ignificant role in the radiogenic heating of Earth-like exoplanet, which can affect the development of a habitable environment on their urface. The initial amount of K 40 in the interior of thee planet depend on the compoition of the intertellar cloud from which they formed. Within thi context, nuclear reaction that regulate the production of K 40 during tellar evolution can play a critical role. Purpoe: In thi tudy, we contrain for the firt time the atrophyical reaction rate of K 40 ( n , p ) Ar 40 , which i reponible for the detruction of K 40 during tellar nucleoynthei. We provide to the nuclear phyic community high-reolution data on the cro ection and angular ditribution of the Ar 40 ( p , n ) K 40 reaction. Thee are important to variou application involving Ar 40 . The aociated reaction rate of the Ar 40 ( p , n ) K 40 proce addree a reaction rate gap in the Joint Intitute for Nuclear Atrophyic REACLIB databae in the region of intermediate-ma iotope. Method: We performed differential cro-ection meaurement on the Ar 40 ( p , n ) K 40 reaction, for ix energie in the center-of-ma ytem between 3.2 and 4.0 MeV and variou angle between 0 ° and 135 ° . The experiment took place at the Edward Accelerator Laboratory at Ohio Univerity uing the beam winger target location and a tandard neutron time-of-flight technique. We extracted total and partial cro ection by integrating the double differential cro ection we meaured. Reult: The total and partial cro ection varied with energy due to the contribution from iobaric analog tate and Ericon type fluctuation. The energy-averaged neutron angular ditribution were ymmetrical relative to 90 ° . Baed on the experimental data, local tranmiion coefficient were extracted and were ued to calculate the atrophyical reaction rate of Ar 40 ( p , n ) K 40 and K 40 ( n , p ) Ar 40 reaction. The new rate were found to vary ignificantly from the theoretical rate in the REACLIB library. We implemented the new rate in network calculation to tudy nucleoynthei via the low neutron capture proce, and we found that the produced abundance of K 40 i reduced by up to 10% compared to calculation with the library rate. At the ame time, the above reult remove a ignificant portion of the previou theoretical uncertainty on the K 40 yield from tellar evolution calculation. Concluion: Our reult upport a detruction rate of K 40 in maive tar via the K 40 ( n , p ) Ar 40 reaction that i larger compared to previou etimate. The rate of K 40 detruction via the K 40 ( n , p ) Ar 40 reaction now ha a dramatically reduced uncertainty baed on our meaurement. Latly, thi reult directly affect the predicted tellar yield of K 40 from nucleoynthei, which i a critical input parameter for the galactic chemical evolution model that are currently employed for the tudy of ignificant propertie of exoplanet.« less

The 23Al(p,γ)24Si reaction is among the most important reactions driving the energy generation in type-I x-ray bursts. However, the present reaction-rate uncertainty limits constraints on neutron star properties that can be achieved with burst model-observation comparisons. Here, we present a novel technique for constraining this important reaction by combining the GRETINA array with the neutron detector LENDA coupled to the S800 spectrograph at the National Superconducting Cyclotron Laboratory. The 23Al(d,n) reaction was used to populate the astrophysically important states in 24Si. This enables a measurement in complete kinematics for extracting all relevant inputs necessary to calculate the reaction rate. Formore » the first time, a predicted close-lying doublet of a 2 +2 and (4 +1,0 +2) state in 24Si was disentangled, finally resolving conflicting results from two previous measurements. Furthermore, it was possible to extract spectroscopic factors using GRETINA and LENDA simultaneously. This new technique may be used to constrain other important reaction rates for various astrophysical scenarios.« less